Can't Get Above 4/10 Quality Score?

I'm having a really hard time getting much more than 4/10 quality score on a lot of my keywords in Google Adwords. It's really frustrating because my website is HIGHLY relevant to each of the keywords that I'm using, but for some reason Google's algorithm doesn't think so.

The website is a2xanxiety -dot- com. We sell an herbal remedy for social anxiety. So all of our keywords are like, "social anxiety remedy," "social anxiety cure," "herbal anxiety relief," etc. The best I've gotten was 7/10 on "social anxiety dating" for whatever reason. But some of the keywords that I think are most relevant can't get any higher than 4/10.

I've divided the keywords into several different ad groups where keywords are grouped into categories based on relevance and then a relevant ad is shown for that whole category. And each ad goes to a different landing page where I include the keyword several times in the sales copy and in the meta keyword and description tags.